JEFFERSON CITY, Mo. -- Missouri voters thought they scored a big win against some of the nation's most notorious puppy mills when they approved strict new dog breeding regulations last year. Now state lawmakers are changing the rules.

A state law aimed at cracking down on disreputable breeders and improving animal care has been overhauled by lawmakers who say the voter-approved version is too costly, and punished legitimate dog-breeders who generate an estimated $1 billion annually in the state. Animal advocates complain elected officials are overruling the will of the people and some are prepared to put the issue on the ballot again next year.

Wayne Pacelle, president of the Humane Society of the United States, said public confidence is undercut when about 100 lawmakers change a law backed by about 1 million voters.

"The effort in Jefferson City is a piece-by-piece dismantling of every core provision," Pacelle said. "It suggests to me that this is an industry that wants deregulation. They want to do things that they want and to heck with the people who care about dogs or consumers as long as there are enough dogs purchased."

Missouri Rep. Jerry Nolte, who represents part of a county that passed the ballot measure, said he voted for the bill because it will help protect dogs by increasing funding for enforcement.

"What I was trying to do was interpret what the voter intent was, and what they wanted to do was to lessen the suffering of these animals," said Nolte, a Republican. "And I believe that this, on balance, will reduce the suffering of these animals."

A spokesman for Democratic Gov. Jay Nixon said Thursday the bill would get a careful review and declined comment on whether he planned to sign it.

Missouri's law passed last November on the strength of residents from heavily populated Kansas City and St. Louis but failed in rural areas where many dog breeders operate. But swayed by breeders who argued the law would close them down and concerned about possible future regulation for other agricultural industries, a bipartisan group of mostly rural lawmakers voted to change most of the law's provisions. For example, a 50-dog cap is scrapped but breeders would pay more to boost state oversight of the industry.

The Humane Society of Missouri and the American Society for the Prevention of Cruelty to Animals were among the animal advocates who pushed for ballot measure, pointing to emaciated and flea-infested dogs that lived in filthy conditions. Even breeders who followed the rules, proponents said, have been allowed to keep dogs in wire cages not much larger than their bodies and exposed to excess heat and cold.

Advocates say more than a dozen states have approved stiffer dog-breeding laws in recent years, and like Missouri, Oklahoma lawmakers are considering changes to that new law.

Many of Missouri's roughly 1,300 licensed breeders pushed back, warning lawmakers the voter-approved law could shutter the industry by limiting the number of the breeding dogs they can own and forcing costly housing upgrades. They said some requirements also could worsen care, including mandating solid floors in indoor enclosures that could slow the draining of fluids and lead to cold and sick dogs.

Critics of the law contend the industry's worst has tainted public perception and blame many problems on unlicensed breeders.

The voter-approved measure "is just going to put the law-abiding, licensed, legitimate, conscientious, caring breeders out of business, and the only ones remaining will be the illegal people already flying under the radar," said Mindy Patterson with the Missouri Federation of Animal Owners.

Over the past decade, several state audits have criticized Missouri's dog regulation efforts. But the state is working to do better, now employing 12 inspectors, who each on average cover a region with 225 licensees. The governor also has proposed adding $1.1 million to the budget to hire more personnel.

Supporters of the voter-approved law said insufficient regulations remained a problem. Last year, the Better Business Bureau in Missouri reported receiving 352 complaints and reports against dog breeders and sellers over three years – including many about ill dogs.

"It is interesting to hear some of the statements that are made now that somehow this industry has been wronged," said Barbara Schmitz, campaign manager for the measure. "This industry has had a very long time to voluntarily correct the problems that exist. They have not done so. Lawmakers have failed to act, and the voters stepped in."

Numerous Missouri breeders raise dogs on their farms, selling puppies through Internet ads and word-of-mouth, while others sell to pet stores and to brokers that buy dogs nationwide.

One of those breeders, Hubert Lavy, said people who wrote the law don't fully understand the business and shouldn't develop rules to regulate it. Lavy, 68, whose family raises Labrador retrievers, Maltese, Yorkshire terriers and French bulldogs, said dogs – like employees – are most productive when treated well.

Outdoor pens are cleaned daily and connected to a building with heaters at Lavy's Tenderheart Kennels in Silex about 70 miles northwest of St. Louis. Indoor cages connect through a doggy door to an elevated outdoor cage and have a coated mesh pattern that allows waste to drain.

The kennel donates some dogs and sells roughly 200 puppies per year to earn about $20,000, Lavy said. He estimates it would cost $50,000 to comply with the voter-approved law, which would include expanding indoor space and building solid floors. However, he said he's more likely to just go out of business if the voter-backed law stands.

"There is a place for what I do. There (are) people who want what I do, and I just don't think they should be able to take it away," Lavy said.